Why Chrome 64-bit is installed in 32-bit Program Files?

The answer is on the Chromium bug tracker (see comments #18 and #26).

In short, the dev team decided to keep things that way because it simplifies the upgrade process when migrating from 32-bits Chrome to 64-bits Chrome. They have not changed it yet because it has no user impact.

For 64 bit &32 bit google chrome, the installation location is C:/Program files(x86) and if you need more verification you can open the task manager and check the following

chrome.exe - shown only for 64bit-Chrome

Chrome.exe*32 - shown only for 32 bit chrome

Because this simplified the upgrade path from 32-bit to 64-bit. When Chrome auto-updated you to 64-bit, the installer need not use multiple program files directories.